Investments in Securities - Trading 1 (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 95,101	$ 136,542
Mortgage-related securities
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	5,321	6,013
Fannie Mae
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,836	2,404
Other agency
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	3,333	3,451
Private-label and other mortgage securities
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	152	158
Total non-mortgage-related securities
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	89,780	130,529
U.S. Treasury securities
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	89,707	130,456
Other securities
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	73	73
Consolidated trusts
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 689	$ 793